DUAL-MODE WIRELESS UNIT WITH TWO SPREAD-SPECTRUM FREQUENCY BANDS

Abstract: The invention provides a dual-band spread-spectrum modulator (101, 103, 105) which uses a single, relatively narrow, synthesizer to serve two operating frequency bands (102, 104). In the lower frequency band, the synthesizer may operate in a high-side injection mode, while in the higher frequency range, the synthesizer may operate in a low-side injection mode. In a preferred embodiment, the lower frequency range may comprise about 1850 to 1990 megahertz, while the higher frequency range may comprise about 2400 to 2483.5 megahertz.

Description: DESCRIPTION Dual-Mode Wireless Unit With Two Spread-Spectrum Frequency Bands Background of the Invention 1. Field of the Invention This invention relates to a dual mode wireless unit which uses two spread-spectrum communication bands. 2. Description of Related Art In spread-spectrum modulation in a wireless telephone system, operation in more than one frequency band can be difficult, due to the wide separation between frequency bands. For example, operation in the 900 megahertz and 1800 megahertz bands could require a synthesizer capable of covering approximately 1,000 megahertz in frequency spectrum. However, in hand-held equipment such as tele¬ phones, it is undesirable to use more than one synthesiz¬ er, or even more than one oscillator, due to increased cost, weight, and related considerations. Accordingly, it would be advantageous to provide a spread-spectrum system in which a single, relatively narrow, synthesizer would serve more than one operating frequency band. Summary of the Invention The invention provides a dual-band spread-spectrum modulator which uses a single, relatively narrow, synthe¬ sizer to serve two operating frequency bands. In the lower frequency band, the synthesizer may operate in a high-side injection mode, while in the higher frequency range, the synthesizer may operate in a low-side injection mode. In a preferred embodiment, the lower frequency range may comprise about 1850 to 1990 megahertz, while the higher frequency range may comprise about 2400 to 2483.5 megahertz. Brief Description of the Drawings Figure 1 shows a dual-mode spread-spectrum modulator with two frequency bands. Figure 2 shows a programmable frequency generator. Description of the Preferred Embodiment Figure 1 shows a dual-mode spread-spectrum modulator with two frequency bands. A first frequency source 101 may generate a first frequency fl 102, while a second frequency source 103 may generate a second frequency f2 104. The first frequency fl 102 and the second frequency f2 104 may be coupled to a multiplier 105, which may generate a bimodal signal 10S with a frequency distribution over two frequency ranges fL 107 and fH 108. In a preferred embodiment, the lower of the two frequencies fL 107 (fL = fl - f2) may range from about 1850 to 1990 megahertz, while the higher of the two frequencies fH 108 (fH = fl + f2) may range from about 2400 to 2483.5 megahertz. When one of the two frequencies fl and f2, e.g., f2 is chosen between the two ranges, e.g., about 2200 megahertz, the other frequency, e.g., fl may be chosen between about 300 and 440 megahertz. The bimodal signal 106 may be coupled to a binary encoder 109, for encoding a data stream 110. The data stream 110, comprising a sequence of data bits 111, may be coupled to the binary encoder 109, which may generate a first frequency, e.g., fL 107, when a data bit 111 in the data stream 110 is a "0" bit, and may generate a second frequency, e.g., fH 108, when a data bit 111 in the data stream 110 is a "1" bit. The present invention also provides for monitoring a frequency in each band (or transmitting to a frequency in each band) at once, because both (fl + f2) and (fl - f2) can be stepped down to the same intermediate frequency with a single local oscillator. When the intermediate frequency is 260 MHz and the local oscillator is set to 2180 MHz, the present invention allows operation at both 1920 MHz and 2440 MHz. When the local oscillator is set 10 MHz greater, the present invention then allows opera¬ tion at both 1930 MHz and 2450 MHz, i.e., two frequencies each 10 MHz greater. Thus for paired frequencies, the present invention allows reception or transmission on either frequency (or both) in the pair. Figure 2 shows a programmable frequency generator. A reference frequency signal 201 may be coupled to a multiplier 202. The multiplier 202 may generate a signal f(s) 203, which may be coupled to a voltage-controlled oscillator (VCO) 204. The VCO 204 may be coupled to an output node 205, which provides an output frequency signal 206, and may also be coupled in a feedback configuration to the multiplier 202 by way of a programmable divide-by-N counter 207. The programmable divide-by-N counter 208 may be programmed by a set of control lines 209. Alternative Embodiments While preferred embodiments are disclosed herein, many variations are possible which remain within the concept and scope of the invention, and these variations would become clear to one of ordinary skill in the art after perusal of the specification, drawings and claims herein. For example, information which is encoded for trans¬ mission is referred to herein as "data", but it would be clear to those of ordinary skill in the art, after perusal of this application, that these data could comprise data, voice (encoded digitally or otherwise) error-correcting codes, control information, or other signals, and that this would be within the scope and spirit of the inven- tion.

Claims: Claims 1. A spread-spectrum modulator having a single frequency synthesizer and operating in a plurality of disjoint output frequency bands. 2. A spread-spectrum modulator, comprising a frequency synthesizer; a multiplier coupled to said frequency synthesiz¬ er; and a binary encoder coupled to said multiplier.

Inventors: DIXON ROBERT C, VANDERPOOL JEFFREY S, DIXON, ROBERT, C., VANDERPOOL, JEFFREY, S.
Applicants: OMNIPOINT CORP, OMNIPOINT CORPORATION
Application year: 1994
Main classification: H04B1
IPC codes: H04B1, H04B7, H04J13, H04L1, H04L27, H04Q7